Experimental measurements of telecentricity errors in high-numerical-aperture extreme ultraviolet mask images

Nontelecentric illumination in extreme ultraviolet (EUV) lithography leads to pattern shifts through focus called telecentricity errors. As the industry moves toward finer pitch structures and higher numerical apertures (NA) to improve resolution, the effects of telecentricity errors become more significant. These telecentricity errors are dependent on pattern pitch, pattern type, lens aberrations, mask stack, to name a few. In this paper, a novel technique to measure telecentricity errors using EUV mask images from an actinic mask inspection tool, called the SEMATECH High NA Actinic Reticle Review Project (SHARP) is presented. SHARP is SEMATECH's second generation actinic mask imaging tool developed by Lawrence Berkeley National Laboratory. The SHARP can image masks at different numerical aperture settings, even beyond the currently available scanner NA of 0.33 (high-NA EUV) and also has a set of programmable illuminator choices. A tuned multilayer EUV mask blank was fabricated with test structures optim...